Moving blade and turbomachine

ABSTRACT

A moving blade for a turbomachine, in particular an aircraft engine, is disclosed, having an inner shroud which has a front elongation for forming an axial overlap with an upstream guide blade, and on which at least one flow guide element for deflecting a leakage flow of a cooling air flow in the peripheral direction is situated. The at least one flow guide element is guided beyond a leading edge of the elongation. A turbomachine having a plurality of these types of moving blades is also disclosed.

This claims the benefit of German Patent Application DE 10 2012 206126.6, filed Apr. 13, 2012 and hereby incorporated by reference herein.

The present invention relates to a moving blade for a turbomachine and aturbomachine.

BACKGROUND

In engine construction it is generally known that the turbine efficiencymay be increased when a leakage flow of a cooling air flow which isbranched off on the compressor side, for example, is introduced into ahot gas flow between the guide blades and the moving blades. This typeof introduction is described in U.S. Pat. No. 7,244,104 B2, for example,which is hereby incorporated by reference herein. In the patent it isproposed to provide a plurality of flow guide elements in the form ofribs or indentations on an upstream or front elongation of a movingblade inner shroud for forming an axial overlap with an upstream guideblade. The flow guide elements are situated on the elongation on the hotgas side, and have a front curved section and a rear axial section onthe hot gas side. The curved sections, which extend away from a leadingedge of the elongation in an axial direction and merge into the axialsections, are oriented in the direction of rotation. The aim is for theflow guide elements to “blade,” in a manner of speaking, the leakageflow from a root-side cavity in the guide blades into the hot gas flow,and to impart a peripheral speed to the leakage flow correspondingapproximately to the peripheral speed of the inner shroud. However, abasic problem in this regard is how the peripheral speed may be impartedto the leakage flow without resulting in a hot gas intake into thecavity on the root side, which could result in overheating of the guideblades and moving blades in the root area.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a moving blade whichallows an optimized introduction of a leakage flow into a hot gas flowand effectively prevents a hot gas intake, as well as a turbomachinehaving improved efficiency.

The present invention provides a moving blade for a turbomachine, inparticular an aircraft engine, has an inner shroud having a frontelongation for forming an axial overlap with an upstream guide blade, onwhich at least one flow guide element for deflecting a leakage flow of acooling air flow in the peripheral direction is situated. According tothe present invention, the at least one flow guide element is guided inthe axial direction beyond a leading edge of the elongation.

As a result of the at least one flow guide element being guided in theaxial direction beyond the leading edge, a speed is imparted early tothe leakage flow in the peripheral direction, and thus in the directionof rotation of the moving blade. The leakage flow is introduced with aswirl into a hot gas flow, thus improving the introduction of theleakage flow. Hot gas intake from the hot gas flow in the direction ofthe cooling air flow is effectively prevented. The at least one flowguide element is preferably integrally formed together with theelongation. The at least one flow guide element may have a linear,curved, wave-like, or other shape. It must be ensured that the flowguide element does not run against an axially opposite guide bladesection due to thermal expansion, so that it may be necessary to enlargean axial distance between the leading edge and the axially oppositeguide blade section.

In one exemplary embodiment, the at least one flow guide element is inflush alignment with a hot gas side and with a cooling air side of theelongation. The at least one flow guide element is thus designed as anaxial finger, in a manner of speaking. When there is a plurality of flowguide elements spaced circumferentially or peripherally apart, theleading edge has a comb-like shape. The finger-like design has theadvantage that, due to the at least one flow guide element, theelongation does not become thicker in the radial direction, but, rather,has a radial extension which has the original thickness or height of theelongation. Thus, an existing radial plate gap is not diminished by theat least one flow guide element, and therefore also does not have to bereset.

In one alternative exemplary embodiment, the flow guide elementprotrudes beyond the hot gas side and beyond the cooling air side in theradial direction. The at least one flow guide element therefore has apaddle-like shape. Compared to the previously mentioned finger-shapedexemplary embodiment, this exemplary embodiment has the advantage thatan effective area of the flow guide element is enlarged. However, forimplementing this paddle-like flow element, structural changes forradial gap maintenance may be necessary to prevent the at least one flowguide element from running against adjacent radial guide blade sectionsor components in the radial direction due to thermal expansion.

In another exemplary embodiment, the at least one flow guide element hasa hot gas side section which is guided on the hot gas side. The flowguide element is thus elongated on the hot gas side in a direction awayfrom the leading edge. The aerodynamic action of the flow guide elementmay be further intensified in this way. Depending on the angular settingof the section on the hot gas side in the axial direction, the leakageflow may be accelerated to a speed in the peripheral direction which isgreater than the peripheral speed of the inner shroud, thus ensuringthat a speed that is less than or significantly less than the peripheralspeed is not imparted to the leakage flow. At the same time, theextension of the at least one flow guide element on the elongationbrings about a structural/mechanical stabilization of the elongation, sothat the elongation has a reduced cross section, at least in the area ofthe flow guide element, and therefore may be designed in aweight-optimized manner. Thus, in this exemplary embodiment the at leastone flow guide element also acts as a reinforcing structure in the formof a rib. Since the at least one rib-like flow guide element radiallyoutwardly thickens the elongation at least in sections, for radial gapmaintenance, structural changes may be necessary which compensate forthe diminished original radial distance. For example, for radial gapmaintenance it may be necessary to radially inwardly offset theelongation.

In another exemplary embodiment, the at least one flow guide element hasa cooling air side section which is guided on the cooling air side. Inthis way, a swirl is already imparted to the leakage flow in the area ofthe cooling air side. For accelerating the leakage flow to a speed inthe peripheral direction which is greater than the peripheral speed ofthe inner shroud, the at least one rib-like flow guide element on thecooling air side opposite from the above-mentioned rib-like flow guideelement on the hot gas side should be angularly set in the axialdirection. Since the at least one rib-like flow guide element radiallyinwardly thickens the elongation at least in sections, structuralchanges may be necessary for radial gap maintenance.

In one exemplary embodiment, the at least one flow guide element has asection on the hot gas side and a section on the cooling air side. Thistype of U-shaped flow guide element has the advantage that the leakageflow is influenced by the at least one flow guide element on the coolingair side, the leading edge side, and the hot gas side.

The section on the hot gas side and the section on the cooling air sideare preferably angularly set oppositely with respect to one another,viewed in the direction of rotation. As a result, the leakage flow onthe cooling air side and on the hot gas side is acted on by a velocitycomponent in the same direction. In particular, the section on the hotgas side is situated in front of the section on the cooling air side,viewed against the direction of rotation.

In particular due to structural-mechanical and production engineeringreasons, it may be advantageous for the section on the hot gas sideand/or the section on the cooling air side to be guided over the entirelength of the elongation. Due to the stabilizing effect of the at leastone flow guide element, it is thus possible to design the elongation tobe thinner, at least in sections, and thus in a weight-optimized manner,so that the rotor mass may be reduced.

From the standpoint of radial gap maintenance, it is advantageous whenthe section on the hot gas side and/or the section on the cooling airside extend(s) in parallel or essentially in parallel to the respectiveradially opposite guide blade section or component. It is thereforepreferred that the section on the hot gas side and/or the section on thecooling air side has/have a constant height. However, the height of theat least one flow guide element may also vary. In that case, however, inorder to not adversely affect the separation effect of the plate gap, itis preferred for the at least one flow guide element to be flat on theother side of the leading edge.

The swirl action or aerodynamic effect of the leakage flow may beadditionally influenced by the number of flow guide elements perelongation. Thus, in one exemplary embodiment, multiple flow guideelements are situated next to one another on an elongation, viewed inthe peripheral direction.

A preferred turbomachine has at least one moving blade row having aplurality of the moving blades according to the present invention. Thistype of turbomachine is characterized by an improved efficiency comparedto a turbomachine having conventional moving blade rows. Significantstructural changes to the components adjacent to this moving blade row,such as guide blade rows and systems, are not necessary. Depending onthe design of the flow guide elements, only minor structural changes arenecessary for gap maintenance or setting the plate gap.

Other advantageous exemplary embodiments of the present invention arethe subject matter of further subclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred exemplary embodiments of the present invention are explainedin greater detail below with reference to greatly simplified schematicillustrations.

FIG. 1 shows a finger-shaped flow guide element, according to thepresent invention, of a moving blade;

FIG. 2 shows a paddle-like flow guide element;

FIG. 3 shows an example of other exemplary embodiments of the flow guideelement according to the present invention;

FIG. 4 shows another paddle-like flow guide element;

FIG. 5 shows a flow guide element having a section on the hot gas side;

FIG. 6 shows a flow guide element having a section on the cooling airside; and

FIG. 7 shows a flow guide element having a section on the hot gas sideand a section on the cooling air side.

DETAILED DESCRIPTION

FIG. 1 shows an axial section of a turbomachine 1 in the area of a guideblade 2 and a downstream moving blade 4. The turbomachine is preferablyan aircraft engine, but may also be a stationary gas turbine. Guideblade 2 is fastened at the root side to a housing section or guide bladesupport ring, and together with a plurality of further guide blades 2forms a stationary guide blade row which surrounds a rotor hub whichrotates about a rotational axis 6. Moving blade 4 is connected at theroot side to the rotor hub via a disk element, for example, and togetherwith a plurality of further moving blades 4 forms a moving blade rowwhich rotates with the rotor hub about rotational axis 6. A direction ofrotation or peripheral direction is indicated by the arrow denoted byreference character u.

Guide blade 2 has a platform 8 which extends from a blade tip 10 andrepresents a radial inner delimitation of a hot gas path. A hot gas flow12 flows axially through the hot gas path (in the x direction). In theexemplary embodiment shown, the hot gas flow flows through turbomachine1 from left to right. In order to stabilize platform 8, the platform hasa plurality of webs 14 situated on a side facing away from blade tip 10.However, if platform 8 has sufficient inherent stability, the webs maybe dispensed with

A radially inwardly directed fastening flange 16 for fastening guideblade 2 to a stationary connecting ring surrounding the rotor hubextends from platform 8. Fastening flange 16 is situated at a distancefrom a trailing edge 18 of platform 8, and together with platform 8delimits an annular space 20. A peripheral plate 22 is connected tofastening flange 16, and delimits annular space 20 in the direction ofthe rotor hub, thus dividing annular space 20 into a radially outercavity and a radially inner cavity.

Moving blade 4 has an inner shroud 24 which is situated between a bladeneck 26 or blade shank and a blade 28, and which represents an innerradial delimitation of the hot gas path. In the exemplary embodimentshown, the inner shroud is situated approximately at the same radialposition as platform 8. Moving blade 4 and guide blade 2 are situatedwith respect to one another in the axial direction in such a way thatbetween trailing edge 18 of platform 8 and an outer end face 30 of innershroud 24 an annular gap 32 is formed, through which a gas exchangebetween hot gas flow 12 and a hub-side cooling air flow may take placein principle. For practically complete structural sealing of annular gap32 in the radial direction (y direction), inner shroud 24 has a frontelongation 34 for forming an axial overlap with guide blade 2 or withits platform 8. Elongation 34 extends from outer end face 30 in thedirection of guide blade 2, and has a length such that it protrudes intoannular space 20, i.e., the outer cavity between platform 8 andperipheral plate 22.

To avoid a hot gas intake, a leakage flow 36 of the cooling air flow isblown through annular gap 32 into hot gas flow 12. According to thepresent invention, at least one flow guide element 38 is provided forintroducing leakage flow 36 with a swirl into hot gas flow 12 or forimparting the peripheral speed of inner shroud 24 to leakage flow 36. Atthe same time, the machine efficiency is improved by the introduction ofleakage flow 36, imparted with swirl, into the hot gas flow.

In the first exemplary embodiment shown in FIG. 1, flow guide element 38is designed as a finger-shaped projection which extends essentially inthe axial direction from a leading edge 40 of front elongation 34. Theprojection, i.e., flow guide element 38, is preferably linear, but mayalso be concave, for example in peripheral direction u. For a pluralityof these types of finger-shaped projections 38, leading edge 40 has acomb-like shape. Flow guide element 38 preferably merges with flushalignment into a hot gas side 42 and into a cooling air side 44 of frontelongation 34. In this exemplary embodiment, the projection thus has thesame radial extension as front elongation 34, so that flow guide element38 does not act on a radial plate gap between elongation 34 and web 14or between elongation 34 and peripheral plate 22. Depending on the axialextension of the at least one flow guide element 38 beyond leading edge40, for the axial gap maintenance an original axial distance betweenleading edge 40 and the fastening flange must be increased.

In one exemplary embodiment shown in FIG. 2, flow guide element 38 isdesigned as a projection on the leading edge side which is guided beyondhot gas side 42 and beyond cooling air side 44 in the radial direction.Thus, this flow guide element 38 has a shape that is paddle-like and inparticular half moon-like. In particular, flow guide element 38 has flatouter surfaces. Flow guide element 38 is preferably not angularly set inaxial direction x and in radial direction y (axial setting angle andradial setting angle=0°). However, it may also be angularly set in axialdirection x and/or in radial direction y (axial setting angle and/orradial setting angle≠0°).

Due to the radial elongation of flow guide element 38 beyond hot gasside 42 and cooling air side 44, compared to the preceding finger-shapedexemplary embodiment according to FIG. 1 the at least one flow guideelement 38 according to FIG. 2 has an enlarged effective area forimparting swirl to leakage flow 36. For radial gap maintenance or toprevent flow guide element 38 from running against web 14 and theperipheral plate due to thermal expansion, it may be necessary toradially inwardly offset elongation 34 and peripheral plate 22 withrespect to the finger-shaped exemplary embodiment according to FIG. 1.Since the at least one flow guide element 38 also extends in thedirection of peripheral plate 22, for an axially symmetrical design offlow guide element 38, peripheral plate 22 must then be radiallyinwardly offset by twice the distance compared to elongation 34.

Further exemplary embodiments of flow guide element 38 are outlined inFIG. 3. In contrast to the above-mentioned exemplary embodimentsaccording to FIGS. 1 and 2, these exemplary embodiments additionallyhave a rib-like extension in the direction of a blade neck 26, i.e., aradially outer end face 30, as well as a radially inner end face 46 ofblade neck 26. In this regard, these flow guide elements 38 have a headsection 48 which extends beyond a leading edge 40 in axial direction x,and a section 50 on the hot gas side and/or a section 52 on the coolinggas side which extend(s) from the head section in the direction of bladeneck 26. As indicated by the dashed lines, sections 50, 52 may extendonly over a length of elongation 34, or may merge into end faces 30, 46.

If sections 50, 52 are guided only over a length of elongation 34, forstructural-mechanical reasons it is preferred that these sections mergeinto hot gas side 42 or cooling air side 44 in a stepless, for exampleramped, manner. If sections 50, 52 extend to blade neck 26, it ispreferred that these sections have a constant height or extension in theradial direction. Due to sections 50, 52, the effective area of the atleast one flow guide element 38 is further increased compared to thesecond exemplary embodiment according to FIG. 2, which has a positiveeffect on the imparting of swirl to leakage flow 36. In addition, incontrast to the preceding exemplary embodiments according to FIGS. 1 and2, flow guide element 38 is stabilized since it surrounds leading edge40.

FIG. 4 shows one exemplary embodiment of flow guide element 38 having asection 50 on the hot gas side and a section 52 on the cooling air sidewhich extend only over a length of an elongation 34. Flow guide element38 surrounds a leading edge 40 in a U-shaped manner, and mergescontinuously into a hot gas side 42 and into a cooling air side 44. Forexample, in the side view flow guide element 38 is a flat circular diskwhich is interrupted by elongation 34 in the area of hot gas side 42 andcooling air side 44. Thus, this paddle-like flow guide element 38 has afull-moon shape, with a head section 48 and two runout sections 50, 52,in a manner of speaking. Due to the elongation of flow guide element 38on hot gas side 42 and on cooling air side 44, for the same extension inthe radial direction this exemplary embodiment has a larger effectivearea than the exemplary embodiment according to FIG. 2.

The at least one flow guide element 38 is preferably not angularly setin axial direction x and in radial direction y. However, it may also beangularly set, i.e., positively or negatively inclined, in axialdirection x or in radial direction y. For radial gap maintenance,elongation 34 and a peripheral plate 22 may be radially inwardly offset,similarly to the exemplary embodiment according to FIG. 2.

FIG. 5 shows one exemplary embodiment of a rib-like flow guide element38 which extends in axial direction x beyond a leading edge 40 of anelongation 34, the flow guide element with its head section 48terminating in flush alignment with a cooling air side 44, and with itssection 50 on the hot gas side being guided to outer end face 30. As aresult, this flow guide element 38 has an L shape in the side view.

Section 50 on the hot gas side preferably has an elongated linear shapewith a constant height. This section is angularly set in axial directionx on a hot gas side 42 of elongation 34. Head section 48 is preferablynot angularly set in axial direction x.

In this exemplary embodiment, the inclination of section 50 on the hotgas side is such that, viewed against direction of rotation u, section50 on the hot gas side is situated in front of head section 48. Thus,starting from head section 48, section 50 on the hot gas side exits theplane of the drawing. Due to the inclination, upon exiting the outercavity, leakage flow 36 is accelerated to a speed u in the peripheraldirection which is equal to or slightly greater than the peripheralspeed of inner shroud 24.

For radial gap maintenance or for preventing flow guide element 38 fromrunning against web 14 and peripheral plate 22 due to thermal expansion,elongation 34 and a peripheral plate 22 may, if necessary, be radiallyinwardly offset with respect to the finger-shaped exemplary embodimentaccording to FIG. 1. Since the at least one rib-like flow guide element38 is situated on the leading edge side and the hot gas side, andtherefore an original radial distance between elongation 34 andperipheral plate 22 is not diminished, peripheral plate 22 may then beradially inwardly offset by the same distance as elongation 34.

FIG. 6 shows one exemplary embodiment of a rib-like flow guide element38 which extends in axial direction x beyond a leading edge 40 of anelongation 34, the flow guide element with its head section 48terminating in flush alignment with a hot gas side 42, and with itssection 52 on the cooling air side being guided to inner end face 46. Asa result, this flow guide element 38 likewise has an L shape in the sideview.

Section 52 on the cooling air side preferably has a constant height anda linear design. This section is angularly set in axial direction x on acooling gas side 44 of elongation 34. Head section 48 is preferably notangularly set in axial direction x.

To accelerate leakage flow 36 to a speed which is approximately the sameas or slightly greater than the peripheral speed of inner shroud 24, inthis exemplary embodiment the inclination of section 52 on the coolingair side is such that, viewed against the direction of rotation, section52 on the cooling air side is situated behind head section 48. Thus,starting from head section 48, section 52 on the cooling air side entersthe plane of the drawing.

For radial gap maintenance, a peripheral plate 22 may, if necessary, beradially inwardly offset with respect to the finger-shaped exemplaryembodiment according to FIG. 1. Since the at least one rib-like flowguide element 38 is situated on the leading edge side and the coolingair side, and therefore an original radial distance between elongation34 and web 14 is not diminished, elongation 34 does not have to beradially inwardly offset.

FIG. 7 shows a top view of an unwound peripheral section of a movingblade row in the area of a front elongation 34 which is provided with afurther exemplary embodiment of flow guide element 38 according to thepresent invention. According to the illustration in FIG. 3, flow guideelement 38 with its head section 48 surrounds a leading edge 40 ofelongation 34 on both sides, and via a section 50 on the hot gas sideand via a section 52 on the cooling air side is guided to outer andinner end face 30, 46, respectively. Sections 50, 52 preferably have auniform constant height and a linear design. These sections are inclinedin axial direction x, and in particular are oriented with respect to oneanother in such a way that that they extend diagonally opposite fromhead section 48 in the direction of end faces 30, 46. Head section 48 ispreferably not angularly set in axial direction x.

In this exemplary embodiment, the inclination of sections 50, 52 is suchthat, viewed against direction of rotation u, section 50 on the hot gasside is situated in front of section 52 on the cooling air side. Thus,starting from head section 48, section 50 on the hot gas side exits theplane of the drawing, and starting from head section 48, section 52 onthe cooling air side enters the plane of the drawing. Thus, in the sideview this flow guide element 38 has a rib-like, in particular V-like,shape with two oppositely pivoted fork sections 50, 52.

A moving blade for a turbomachine, in particular an aircraft engine, isdisclosed, having an inner shroud which has a front elongation forforming an axial overlap with an upstream guide blade, and on which atleast one flow guide element for deflecting a leakage flow of a coolingair flow in the peripheral direction is situated, the at least one flowguide element being guided beyond a leading edge of the elongation, anda turbomachine having a plurality of these types of moving blades.

LIST OF REFERENCE NUMERALS

-   1 turbomachine-   2 guide blade-   4 moving blade-   6 rotational axis-   8 platform-   10 blade tip-   12 hot gas flow-   14 web-   16 fastening flange-   18 trailing edge-   20 annular space-   22 peripheral plate-   24 inner shroud-   26 blade neck-   28 blade-   30 outer end face-   32 annular gap-   34 front elongation-   36 leakage flow-   38 flow guide element-   40 leading edge-   42 hot gas side-   44 cooling air side-   46 inner end face-   48 head section-   50 section on the hot gas side-   52 section on the cooling air side-   x axial direction-   y radial direction-   u peripheral direction or direction of rotation

What is claimed is:
 1. A moving blade for a turbomachine comprising: aninner shroud having a front elongation for forming an axial overlap withan upstream guide blade; at least one flow guide element for deflectinga leakage flow of a cooling air flow being situated in a peripheraldirection, the at least one flow guide element extending in an axialdirection beyond a leading edge of the elongation.
 2. The moving bladeas recited in claim 1 wherein the flow guide element terminates in flushalignment with a hot gas side and with a cooling air side of theelongation.
 3. The moving blade as recited in claim 1 wherein the flowguide element protrudes beyond a hot gas side and a cooling air side ofthe elongation in the radial direction.
 4. The moving blade as recitedin claim 1 wherein the flow guide element has a hot gas side section ona hot gas side of the elongation.
 5. The moving blade as recited inclaim 4 wherein the hot gas side is located over an entirety of an axialextension of the elongation.
 6. The moving blade as recited in claim 4wherein the hot gas side section has a constant height.
 7. The movingblade as recited in claim 1 wherein the flow guide element has a coolingair side section on a cooling air side of the elongation.
 8. The movingblade as recited in claim 7 wherein the cooling gas side is located overan entirety of an axial extension of the elongation.
 9. The moving bladeas recited in claim 7 wherein the cooling gas side section has aconstant height.
 10. The moving blade as recited in claim 1 wherein theflow guide element has a hot gas side section on the hot gas side of theelongation, and a cooling air side section on a cooling air side of theelongation.
 11. The moving blade as recited in claim 6 the hot gas sidesection and the cooling air side section are oriented oppositely withrespect to one another, viewed in a direction of rotation.
 12. Themoving blade as recited in claim 10 wherein the hot gas side and/or thecooling air section is located over an entirety of an axial extension ofthe elongation.
 13. The moving blade as recited in claim 10 wherein thehot gas side section and/or the cooling air side section has a constantheight.
 14. The moving blade as recited in claim 1 wherein the at leastone flow guide element includes a plurality of flow guide elements. 11.A turbomachine comprising: a moving blade row having a plurality ofmoving blades as recited in claim
 1. 12. An aircraft engine comprisingthe turbomachine as recited in claim 11.